New chemical approaches involving polyfunctionalized C-ribosyl derivatives as versatile intermediates for the syntheses of ten classes of C-nucleosides are described. Additionally, conversion of commercially-available as well as synthetic C-nucleosides to new analogs will be undertaken. The classes of synthetic C-nucleosides proposed are structural analogs (or isosteres) of the nucleosides of the nucleic acids and/or of the naturally-occurring pyrimidine and "purine-like" nucleoside antibiotics. Included in these classes are ribo, 2-deoxyribo, or arabino C-nucleoside derivatives bearing such aglycons as pyrimidines, pyrazoles, pyrazolo-triazines, triazolo-triazines, pyrrolo-pyrimidines and thieno-pyrimidines. Rationales are offered which are based a) on the demonstrated anti-cancer activities of some related C-nucleosides recently synthesized in our laboratory and b) on biochemical considerations. "In-house" biochemical and biological collaborative studies for the proper evaluation of the target C-nucleosides are described briefly. Relationships between chemical structure and anti-cancer activity should be ascertainable from these investigations.